Cotton fiber consists of a primary and a secondary cell wall. The secondary cell wall is practically pure cellulose, whereas the primary cell wall is a complex lattice of pectin, protein, waxes, pigments, hemicellulose and cellulose. In textile scouring of cellulosic material (e.g. knitted or woven cotton fabric) alkaline conditions (up to 10% NaOH) and high temperatures (up to 100° C.) are needed for effective removal of primary cell wall components. This harsh chemical treatment results in raw material losses and in substantial environmental burden. There are several different enzymes that have the ability to degrade pectin; these are the pectinases, pectin methylesterases, pectin lyases and pectate lyases.
“Size” is the name given to the substance or mixture of substances that is applied to the warp thread before weaving. The size forms a coating around the surface of the thread before weaving. This coating provides the lubrication and prevents the breakage of warp thread during the weaving operation. Some common chemicals used to prepare sizes are Polyacrylic Acid (PA), Polyvinyl Alcohol (PVA), Starch, and Modified Starch. Cellulosic fibers including cotton, rayon and blend of these with synthetic fibers such as polyester, is usually sized with starch-based sizes. Desizing process removes the size before dyeing, printing and/or finishing. Starch sizes can be removed by hot acid wash, which will hydrolyze starch. However, acid hydrolysis results in loss of raw material since cellulose is also prone to acid hydrolysis. Starch sizes can also be removed by using hydrogen peroxide to degrade starch by oxidation. Desizing can also be an enzymatic process. Amylases have been used for many years in textile industry for removal of starch sizes. Conditions (e.g., pH and temperature) for enzymatic desizing are dictated by the operating conditions of the enzyme. Most amylases used in the application are relatively thermostable, however, they are neutral or acidic optimum enzymes.
“Scouring” is a process in which desized cotton fabric is processed to solubilize and extract undesired non-cellulosic material naturally found in cotton and also to remove applied impurities such as machinery lubricants. Scouring uses highly alkaline chemicals to remove the non-cellulosic material, which has a serious environmental impact. Additionally, the chemicals partially degrade the cellulose in the cotton fiber which causes a loss of fiber strength and raw materials and as such is a non-optimal process. The final step in the cotton fabric pretreatment process is bleaching in which the natural pigments and matter present in the fiber are bleached. A thermostable alkaline pectinolytic enzyme that could target specifically the non-cellulosic material could reduce or eliminate the use of harsh chemicals lessening the burden on the environment while maintaining the integrity and strength of the cotton fiber.